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Message started by axa on 04/27/16 at 15:22:42

Title: advice on bent cylinder bolts.
Post by axa on 04/27/16 at 15:22:42

Anyone have any experience in changing the cylinder bolts.
Ive had this project bike transmission out, top end off, on a bench for some time now.
I was cleaning up one day when i knocked it off its 2' high bench exactly on to the the cylinder bolts and it just stood there...

well of course now the longer bolts are bent nearly as much as the short ones are tall.

Are these just a screw out or does the case need to be cracked open?

Now Im trying to figure out if i need 2 or 4 new bolts, or if i can i use this sort of process to bend then straighten them out.
https://www.youtube.com/watch?v=mRtIxG2co5w

Last time i asked this type of question about push rods, i got the horde into a flame war about the feasibility of such a thing.
In the end I conclude that its not feasible for push rods, but im not looking to start another flame war about this here.

I cant imagine too many idiots end up bending their bolts and have this experience, but if you do by all means let us know what happened

Title: Re: advice on bent cylinder bolts.
Post by justin_o_guy2 on 04/27/16 at 15:42:46

That's gonna fall( no pun intended ) in the
I've never heard that one before
category.
I don't know that answer.
I am curious about what your broom weighs, though.

Title: Re: advice on bent cylinder bolts.
Post by gizzo on 04/27/16 at 17:02:14

I think I'd pull the bolts out (lock a couple of nuts together on the top thread and screw it out) and try to straighten them first. That YouTube method looks doable. If you have access to a hydraulic press, too easy. You have nothing to lose by trying. Then if you have to, you can still buy new studs. If they can be straightened nicely, I'd be reusing them. But yeah, pushrods, not so much :D.

Title: Re: advice on bent cylinder bolts.
Post by engineer on 04/27/16 at 17:31:05

They just screw in. Go to Bikebandit.com or some similar site and look it up in the OEM parts section for the cylinder. They are about $8 apiece so two of them won't break the bank. However, if you want to straighten them it is not a big deal unless they are bent more than a few degrees or they are bent at the threads or at the point where the threads end and the smooth shank begins.

Straightening them is easy and you don't need a dial indicator to get them straight enough. BUT, when they are bent and you bend it back again you are doing a little bit of "work hardening". On the smooth shank that's not much of a problem but it might be at the threads. The threads already make a stress point with their sharp V cuts into the stud body and a sometimes they break there, or weaken and break later, like maybe when you torque them down.

I've straightened lots of fasteners and if the angle of the bend is shallow and the steel is a good it usually works. But I would never do it to something that is critical to safety.

Title: Re: advice on bent cylinder bolts.
Post by gizzo on 04/27/16 at 17:46:48

Ha ha $8. Go buy new ones!! You'd spend more time trying to get a good result than if you'd gone to work to earn the money.

Title: Re: advice on bent cylinder bolts.
Post by justin_o_guy2 on 04/27/16 at 18:14:00

I am one cheap SOB, I straighten nails and drill bits and bolts.
But I would not straighten those. A problem there is gonna be a lot worse than the cost of new. Before you order, pull all of them, roll them on a known flat something.. I keep a thick piece of glass, because I straighten stuff, check all of them out.
I'd be looking closely at the case, where they go in.
Any distortion needs to be carefully worked flat. A good file.
Don't let stuff get in the engine.

A straight edge is your friend.

Title: Re: advice on bent cylinder bolts.
Post by axa on 04/28/16 at 10:16:49

i know its a critical application, a safety issue but being a cheap bastard as well I thought id ask. ya i can get a new set of bolts for 40$, i suppose the question is if i need just the 2 or all 4...

Title: Re: advice on bent cylinder bolts.
Post by justin_o_guy2 on 04/28/16 at 10:28:58

Pull them, roll them, see. If it's not visible without rolling, then it's not hurt, but if it's not Straight, then when you are torquing it, how much of the clamping force pulling it straight? Will it slowly yield to the tension and relieve some of the clamping force?
Sometimes saving money today costs more tomorrow.
I'm cheap, but if there is any question about the quality of a critical element that replacing costs so little, compared to having to go back, new head gasket, and then the bolts you should have replaced?

And, take a bolt to the industrial supply house, the one that supplies the hardware stores in town. It's not gonna be eight bucks. Probably not three.
It's not That special of a bolt. I would be surprised if it's not just a grade eight.

Some places spec a bolt be oiled before torque, some, I think, say clean and dry. If it's supposed to be lubed, and since it's steel in aluminum, I expect it is, make sure you have the hole cleaned out and don't let it get oil in it. You Can screw down onto a puddle of oil and it can stop the bolt. Just oil the bolt, wipe around with fingers.

Title: Re: advice on bent cylinder bolts.
Post by gizzo on 04/28/16 at 14:36:59

706F696E73744575457D6F63281A0 wrote:

And, take a bolt to the industrial supply house, the one that supplies the hardware stores in town. It's not gonna be eight bucks. Probably not three.
It's not That special of a bolt. I would be surprised if it's not just a grade eight.

They are a little bit special: the shanks are waisted so the through hole can double as an oilway. Put a normal bolt in there and you'd lose or at least severely restrict the oil supply to the top end.

Title: Re: advice on bent cylinder bolts.
Post by justin_o_guy2 on 04/28/16 at 14:38:10

Well, in that case, eight bucks isn't a ripoff.
That's why I carry one in. If it's not the same, it's Not the same.
Might save money by trying.

Title: Re: advice on bent cylinder bolts.
Post by Dave on 04/29/16 at 04:26:14

I would think that somebody on this forum has an old engine case laying around and can get you some used cylinder studs.

Try placing a "Wanted" listing in the Marketplace.

Title: Re: advice on bent cylinder bolts.
Post by axa on 05/02/16 at 06:09:22

thanks for all the advise... id like to get back to this project sometime this spring...